Function mp_rat_read_string

pub unsafe extern "C" fn mp_rat_read_string(
    r: mp_rat,
    radix: mp_size,
    str_: *const c_char,
) -> mp_result

Sets r to the value represented by a zero-terminated string str in the format "n/d" including a sign flag. It returns MP_UNDEF if the encoded denominator has value zero.